/* FCE Ultra - NES/Famicom Emulator
 *
 * Copyright notice for this file:
 *  Copyright (C) 2002-2012 Xodnizel, Zeromus
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * VRC3
 *
 */

#include "mapinc.h"

static uint8 IRQx; //autoenable
static uint8 IRQm; //mode
static uint16 IRQr; //reload

static DECLFW(Mapper73_write) {
	switch (A & 0xF000) {
	case 0x8000: IRQr &= 0xFFF0; IRQr |= (V & 0xF) << 0;  break;
	case 0x9000: IRQr &= 0xFF0F; IRQr |= (V & 0xF) << 4;  break;
	case 0xa000: IRQr &= 0xF0FF; IRQr |= (V & 0xF) << 8;  break;
	case 0xb000: IRQr &= 0x0FFF; IRQr |= (V & 0xF) << 12; break;
	case 0xc000:
		IRQm = V & 4;
		IRQx = V & 1;
		IRQa = V & 2;
		if (IRQa) {
			if (IRQm) {
				IRQCount &= 0xFFFF;
				IRQCount |= (IRQr & 0xFF);
			}else
				IRQCount = IRQr;
		}
		X6502_IRQEnd(FCEU_IQEXT);
		break;
	case 0xd000: X6502_IRQEnd(FCEU_IQEXT); IRQa = IRQx; break;
	case 0xf000: ROM_BANK16(0x8000, V); break;
	}
}

static void Mapper73IRQHook(int a) {
	uint32 i;
	for (i = 0; i < a; i++) {
		if (!IRQa) return;
		if (IRQm) {
			uint16 temp = IRQCount;
			temp &= 0xFF;
			IRQCount &= 0xFF00;
			if (temp == 0xFF) {
				IRQCount = IRQr;
				IRQCount |= (uint16)(IRQr & 0xFF);
				X6502_IRQBegin(FCEU_IQEXT);
			}else {
				temp++;
				IRQCount |= temp;
			}
		}else {
			//16 bit mode
			if (IRQCount == 0xFFFF) {
				IRQCount = IRQr;
				X6502_IRQBegin(FCEU_IQEXT);
			}else
				IRQCount++;
		}
	}
}


void Mapper73_init(void) {
	SetWriteHandler(0x8000, 0xffff, Mapper73_write);
	MapIRQHook = Mapper73IRQHook;
	IRQr = IRQm = IRQx = 0;
}

